I know, I played this way vs assassins and they where a pain to deal with. Right now assassins have their full potential from withever direction they attack you. I say limit that to the backside. The character movement is mouseclick, so one mouseclick and your character has turned around 180 degrees, while the assassin has to walk around you, because of player collision, to get his max damage. It's just a matter of balance. I say let ppl only do maximum damage from the back, that way only the ppl who manage to spent most time at the rear or back of the oponent do the most dmg, and are therefore the better players.
You can also balance assassins to have weapons that are better for penetrating heavy armor and weapons that are more efffective at slicing up clothies. Make it more situational.